Retinal degenerations represent one of the important causes of human blindness. Their prevention and eventual treatment requires understanding the cellular and molecular mechanisms responsible for the survival and differentiation of retinal neurons and photoreceptors. Our goal is to investigate these biological phenomena. These investigations will be carried out both in vivo and in vitro, taking advantage of a recently developed cell culture system which allows survival and differentiation of chick embryo neurons and cone photoreceptors. A variety of analytical techniques will be used, including phase contrast microscopy, time-lapse video recording, scanning and transmission electron microscopy, immunocytochemistry, autoradiography, and fluorescent photobleaching recovery. Using these methods, the role of the cytoskeleton and plasma membrane in the development and maintenance of photoreceptor organizaation will be studied. Treatments promoting survival and differentiation of photoreceptor cells will be investigated, with emphasis on pigment epithelium--derived materials and the vitamin A derivative 11-cis retinal. Finally, the possibility to obtain enriched photoreceptor populations by treating the cultures with toxins known to affect selectively other retinal neurons will be studied. Results from these studies should help us to understand not only normal photoreceptor development and function, but also the mechanisms leading to their disease and degeneration.